Valve Pit l Vacuum Mains l Vacuum Station

The AIRVAC vacuum station is similar in function to a gravity sewer lift station. Sewage is collected in an enclosed wet-well (collection tank) and sewage pumps then transfer the sewage through a force main to the treatment plant. Vacuum pumps create a vacuum on the collection tank which is then transferred to the entire piping network via the vacuum mains which are connected to the collection tank.

AIRVAC's packaged vacuum stations consist of two or more vacuum pumps, two sewage pumps, a collection tank and controls . Units arrive at the job site pre-piped, pre-wired and factory tested to minimize construction costs.

The vacuum station skid is housed in a protective structure designed to fit the characteristics of the neighborhood. A standby generator keeps the vacuum system in operation during extended power outages.

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Vacuum Pumps

The vacuum pumps maintain the system vacuum in the 16” to 20” mercury vacuum (-0.5 to –0.7 bar) operating range. Vacuum pumps do not run continuously; rather the operation is cyclical. Typical run times are 2 to 3 hours per day per pump (4 to 6 hours total).

As sewage and atmospheric air enter the system during valve cycles, system vacuum will gradually decrease from 20” to 16” Hg. The vacuum pumps are sized to bring the vacuum level back to 20” Hg within 3 minutes time. Typical vacuum pump sizes are 10, 15 and 25 horsepower (7.5, 11 and 18.7 Kw). Rotary vane pumps are typically used. .

Sewage pumps

Two, non-clog, dry- pit, horizontal, centrifugal sewage pumps each capable of pumping design peak flow, are used. Dry pit submersible pumps can also be used.

Collection tank

The collection tank is steel or fiberglass and is sized according to peak design flow. Typical sizes range from 1000 to 6000 gallons (3.8 to 22.7 m3). The incoming vacuum mains individually connect to the tank, effectively dividing the collection system into zones.

Controls

The electrical controls are housed in a NEMA Type 12 enclosure which generally is mounted on the equipment skid. Control panels can use either relay-logic or PLC logic. The panel includes motor starters, control relays, pilot lights, hand-off-auto (HOA) switches and hour-run meters.

To monitor system performance, a 7-day chart recorder is installed in the enclosure. In addition, an automatic telephone alarm dialer is provided to alert the operator of alarm conditions.